Shed-forming device for a weaving machine

ABSTRACT

A shed-forming device has elastically deformable selection elements ( 1 ) ( 28   a )-( 28   f ) which can be placed in an undeformed position or in a deformed position, electromagnetic selectors ( 2 ) which can be actuated in order to place or keep each selection element ( 1 ) in successive weaving cycles in one of said positions, and presenting means ( 3 ) in order to mechanically deform selection elements ( 1 ) in the direction of a selector ( 2 ) in each weaving cycle into a presenting position in which they are kept at a distance from the selector ( 2 ) by a stop ( 4 ), and also relates to a method for positioning selection elements of a shed-forming device in this manner.

The present invention relates to a shed-forming device for a weavingmachine comprising a number of elastically deformable selectionelements, it being possible to optionally place each selection elementin an undeformed position or in a deformed position in order todetermine the position of at least one warp thread, a number ofelectromagnetic selectors which can be actuated in order to place orkeep each selection element in successive weaving cycles in one of saidpositions, so that the warp threads are positioned in accordance with apredetermined weaving pattern, and presenting means which are designedto exert a mechanical force on a number of undeformed selection elementsin each weaving cycle, as a result of which said selection elements aredeformed in the direction of an associated selector.

When weaving a fabric on a weaving machine, the warp threads arepositioned with respect to the level at which a pick thread isintroduced in each cycle during the successive weaving cycles. Thepositions of the warp threads in the successive weaving cycles are inthis case determined in such a manner that the weaving process resultsin a fabric having a predetermined weaving pattern. This positioning ofwarp threads with respect to the pick introduction level on a weavingmachine, referred to as the shed formation, is automatically realized bymeans of a shed-forming device.

With a known shed-forming device of the jacquard type, each warp threadto be positioned passes through a heddle eyelet of a heddle. At thebottom, each heddle is connected to a retracting spring which exerts adownwardly directed force on the heddle and, at the top, is connected,via a harness cord, to the end of a tackle cord of a tackle system,which end is situated at a higher level. The tackle system comprises twohooks which are displaceable in the vertical direction. The position ofthese cooperating hooks determines the height of the end of the tacklecord, and thus also of the heddle eyelet and the warp threads passingthrough the latter.

Each hook can be displaced in the vertical direction by a respectiveknife. These two knives are driven so as to move in a up and down movingmanner in opposite phases with respect to one another. Each hookcomprises an elastically deformable portion, referred to as a selectionelement, which can be brought in a non-selection position or a selectionposition by actuating an electromagnetic selector. In the selectionposition, the selection element engages in a fixed hook-shapedprojection as a result of which the hook is kept at a fixed height andis thus not caught by its knife. If the selection element is in thenon-selection position, it cannot engage in the hook-shaped projectionand the hook is caught by a downwardly moving knife. By positioning thehooks in the successive weaving cycles in this manner, a warp thread canbe brought into the required successive positions via the tackle cordand the heddle in order to produce a fabric with the desired weavingpattern.

There are also shed-forming devices which comprise a flexible stripwhich is arranged at a fixed height and can be deformed by anelectromagnetic selector and can thus be positioned with respect to ahook. This type of selection elements can optionally be brought into aselection position in which an associated hook can be attached to theselection element and is retained at a fixed height, or can be broughtinto a non-selection position in which said hook is not retained by theselection element and caught by a knife.

The electromagnetic selectors comprise a solenoid consisting of a coreof magnetisable material around which electrically conducting coils arewound and one or more poles. The unit usually has a plastic housing.When an electric current flows through the coils, a magnetic flux isgenerated so that a deforming magnetic force is exerted on an associatedselection element via one or more force-exerting poles of the selector.

By actuating the selector in order to optionally magnetically influenceand deform a selection element, the selection element may be broughtinto the desired selection position or non-selection position.

It is known to provide shed-forming devices with presenting means whichpush the undeformed selection elements in each weaving cycle slightly inthe direction of their respective selector, so that the magneticallyinfluenceable parts of said selection elements are brought closer to theforce-exerting poles. This results in an airgap between the magneticallyinfluenceable parts of the selection elements and the selector poleswhich is less wide, and consequently less electrical energy is requiredto deform the selection elements.

This results in a reduction in the energy consumption of the numerousselectors in the shed-forming device. This is the case, inter alia, withthe shed-forming device according to EP 0 529 025, where the elasticallydeformable selection elements are pushed in the direction of theselector by a reciprocating knife.

In such a jacquard machine, the chain of cooperating components in ashed-forming device: heddle, retracting spring, harness cord, tackle,selector, hook and hook-guiding means, is present numerous times. Allthese components have geometric deviations which are the result of, forexample, inaccuracies during production and/or not having beenaccurately positioned and/or having been subjected to mutually differentactions of forces, and consequently, the positions of these componentsare not determined exactly and show relatively large differences betweenone another. This applies in particular for the position of the variousselection elements when these have been deformed in the direction of theselector by the presenting means.

This results in the selection elements being presented in mutually verydifferent positions with respect to the associated selector poles, as aconsequence of which the widths of the airgaps between differentselection elements and the associated selector poles differ greatly fromone another. This inaccurate positioning leads to errors in theselection of selection elements, resulting in weaving errors and weavingmachine down time. The reliability of these shed-forming devices thusleaves something to be desired. In order to increase this reliability,it is possible to generate a higher magnetic flux, but this in turnresults in an increased energy consumption.

It is an object of the present invention to remedy the abovementioneddrawbacks by providing a very reliable and also energy-savingshed-forming device.

This object is achieved by providing a shed-forming device having thefeatures indicated in the first paragraph of this description, in which,according to the present invention, the presenting means are designed tomechanically deform the selection elements until they reach a presentingposition in which they are kept at a distance from an associatedselector by a stop.

The presenting means according to the present invention may beconfigured as movable elements which exert a mechanical force on thefixedly secured selection elements while they move, but may also beconfigured as fixedly secured elements with the selection elementsmoving and striking against the fixedly secured presenting means, sothat the fixed presenting means exert a deforming mechanical reactionforce on the moving selection elements. An embodiment in which both thepresenting means and the selection elements move and move with respectto one another can also be produced.

The selection elements are preferably configured as strips or thin bandsof flexible material, and usually also comprise openings to give theselection elements an ideal flexibility and reaction time.

In the context of the present invention, a stop is any obstacle ordetaining means, irrespective of its position, which is arranged in sucha manner or connected to the selection element in such a manner that itcan limit the freedom of movement of a selection element to such adegree that this selection element is kept at a well-defined distancefrom the selector. According to the present invention, a stop doestherefore not necessarily have to be provided on the selection elementor on the selector or in the vicinity of the selector poles. A stop mayalso form part of another part or of a separate part, irrespective ofits position with respect to the selector poles. Detaining means whichare connected to the selection element and retain it when it has reacheda well-defined position with respect to the selector may also fulfilthat role and can thus be regarded as a stop.

By presenting all selection elements in a presenting position which isonly determined by the position of a stop, the position of the presentedselection elements with respect to their respective selector poles is nolonger influenced by the abovementioned said deviations in geometry,position and load of the different components of the device. Saidpositioning is consequently much more accurate, so that the selectionelements are presented in an essentially identical position with respectto the associated selector poles. This results in airgaps for thedifferent selection elements which are far less different from oneanother, thus rendering said shed-forming device much more reliable thanthe known shed-forming devices which provide a presentation of elasticselection elements. In other words, this greatly increases the certaintythat the applied electrical power is sufficient to place the selectionelement in the desired position compared to the known shed-formingdevices.

For the sake of clarity, it should be stressed here that theelectromagnetic selector can already be actuated before the presentationof the selection elements has finished. This is due to the fact that itis important for the presentation that the selection elements ultimatelyend up in a position in which it is quite certain that the appliedelectrical power is sufficient to place or keep the selection elementsin the desired position. In this case, the time at which the selectorcoil is energized is completely immaterial.

The presentation of the selection elements leads to a reduction of theenergy consumption, as the width of the airgap is made smaller. Thus, byplacing each stop in such a manner that the magnetically influenceableparts of the selection elements placed in the presenting position are ata very small distance from the selector poles, a shed-forming device isproduced which is also very energy-saving.

If more selection elements are presented by the same pushing means whichimposes a similar movement trajectory on these selection elements or bydifferent pushing means which move according to an identical movementtrajectory, then the selection elements, due to the abovementioneddeviations in shape and position, will not simultaneously come intocontact with their stop, but at different points in time. This meansthat it has to be ensured that the movement trajectory is sufficientlylong to push all selection elements against a respective stop. Afterall, the presentation movement has to be continued until eventually thelast selection element also bears against a stop. This results in theselection elements which have come into contact with their stop soonerbeing pushed in the direction of their selector with a greater forcethan is required to bring the selection element into contact with itsstop, as a consequence of which they are deformed further. In thepresent patent application, this is referred to by the term‘overpresenting’ or ‘overpresentation’.

In a first, particularly preferred embodiment, the shed-forming deviceaccording to the present invention comprises at least one reciprocatingknife and a number of shed-forming elements which can be caught by aknife in successive weaving cycles in order to change the position ofone or more warp threads, while each selection element is arranged at afixed height and is designed to retain an associated shed-formingelement at a fixed height, and while each selection element is designedto, in the one position, retain the associated shed-forming element at afixed height and, in the other position, not to retain said shed-formingelement and allow it to move along with a knife.

Such a shed-forming device uses, for example, selection elements whichare configured as thin elastically deformable bands or strips made froma material which is magnetically influenceable, and are fixedly securedat one end and extend next to an electromagnetic selector from said end.By optionally energizing the associated selector, each selection elementcan be brought to one or the other position in order to retain anassociated shed-forming element (such as a hook) optionally at a fixedheight.

The selection elements are, for example, provided with hook-engagementmeans which can cooperate in the selection position with complementaryhook-engagement means on the shed-forming element, so that theshed-forming element is retained at a fixed height. The selectionelements may, for example, be provided with a hook-engagement openinginto which a hook-shaped portion or a projection of a shed-formingelement can hook. Conversely, the shed-forming elements may alsocomprise an opening, while the selection elements are provided with ahook-shaped portion or a projection.

In a second, particularly preferred embodiment, said shed-forming devicecomprises at least one reciprocating knife, while each selection elementforms part of a shed-forming element which can be caught by a knife insuccessive weaving cycles in order to change the position of one or morewarp threads, and while each shed-forming element is designed to beretained at a fixed height in the one position of the selection elementand to be caught by a knife in the other position of the selectionelement.

Such a shed-forming device makes use, for example, of selection elementswhich are configured as thin, elastically deformable bands or stripsmade from a magnetically influenceable material, and with one end arefixedly secured to or form part of a reciprocating shed-forming element,while the other end is free. The selection element can thus be anelastically deformable portion of a shed-forming element.

During the movements of the shed-forming element which are imposed bythe knife, the selection element reaches a position in each weavingcycle in which it extends next to an electromagnetic selector. In thisposition, the selection element can be brought from one position to theother position by actuating the associated selector. At a fixed height,hook-engagement means are, for example, provided into which selectionelements which have been brought into the one position engage so thatthe shed-forming elements connected thereto are retained at a fixedheight. In the other position, the selection elements cannot engage intothese hook-engagement means.

In the shed-forming device according to the present invention, therespective selectors are preferably provided with a stop having acontact area which faces an associated selection element, so that eachselection element bears against the contact area of a stop of anassociated selector when it is placed in the presenting position and isthus kept at a distance from a pole surface of said selector.

In this shed-forming device, it is also possible to provide therespective selection elements with a stop having a contact area facingthe associated selector, so that each selection element, when it isplaced in the presenting position, bears against an associated selectorwith the contact area of its stop and is thus kept at a distance from apole surface of said selector.

The overpresentation of a selection element results in the selectionelement being deformed further in the direction of the selector than isrequired (i.e. further than is required to come into contact with itsstop). In this case, the selection element is bent while it bearsagainst the stop. The stop acts as a support and divides the selectionelement into two portions, as it were: the portion on which the force isexerted in order to deform the selection element in the direction of theselector and the other portion which, situated on the other side of thestop, is connected, for example, to a fixedly secured part or to areciprocating shed-forming element. Exerting said force causes theselection element to assume a bent shape with the stop as support, andin order to reach said position, the portion on which the force is beingexerted moves towards the selector poles, while the other portion movesaway from the selector poles.

By overpresenting, the portion on which the force is exerted is thusmoved towards a selector pole so that the intermediate airgap becomesnarrower. The magnetic force which is exerted on the selection elementin said spot will thus increase. In order to ensure that thisoverpresentation has virtually no effect on the total magnetic forcewhich is exerted on the selection element via the selector poles, thestop is placed in such a manner that its contact area is situated in thespace between the parallel transverse planes which delimit the zone ofthe force-exerting pole surfaces.

The contact area of the stop is then provided in the zone of the polesurfaces when the stop is provided on the selector, or is provided inthe presenting position adjoining this zone if the stop is provided onthe selection element. Consequently, overpresenting causes the portionof the selection element on which the force is exerted to come closer toa pole surface, while the other portion, on the other side of the stop,is taken further from a pole surface due to the bending of the selectionelement. The average airgap width or the air volume between themagnetically influenceable parts of the selection elements on the onehand and the associated selector poles on the other hand thus remainsapproximately similar, so that the total magnetic force as well onlychanges very little or not at all.

Preferably, each stop is placed in such a manner that its contact areais situated in a central part of said space, with said central partlying centrally between said transverse planes and being delimited bytwo parallel boundary surfaces having an intermediate distance which ishalf the intermediate distance between said transverse planes.

The magnetically influenceable parts of the selection element which aresituated on either side of the stop opposite a pole surface can thushave approximately the same length. If the overpresentation causes acertain decrease in the air volume on one side of the stop, a virtuallyidentical increase in air volume is produced on the other side of thestop. The total air volume between the magnetically influenceable partsof the selection elements on the one hand and the associated selectorpoles on the other hand thus changes very little, so that the influenceof the overpresentation on the total magnetic force which is exerted onthe selection elements is very limited.

In a preferred embodiment, the contact area of the stop is asubstantially convex surface. As a result thereof, there is a minimalcontact area between the selection element and the stop (if this isprovided on the selector) or between the selector and the stop (if thisis provided on the selection element) and making and breaking thecontact as well as the further deformation of a selection elementbearing against the stop, inter alia in the case of overpresentation,can be effected in a very smooth manner with a minimum of wear and lossof energy.

Said contact area can be completely or partly convex. Preferably, thesurface is convex along the longitudinal direction of the selectionelement. A convex shape along a direction at right angles to thislongitudinal direction enables good contact if the pole surface of theselector and the contact area of the selection element do not runperfectly parallel according to said perpendicular direction. Inaddition, the position of the contact is better defined, as a result ofwhich the physical behaviour of the selection element is unambiguouslydetermined, as the lengths between holding point and contact point, andbetween contact point and free end, are fixed. However, a convex shapealong these two mutually perpendicular directions or according to one ormore other directions is also possible. A surface which is completely orpartly spherical is most advantageous.

In an ideal shed-forming device, the different selection elements aredeformed until they just reach the stop during their presentation, sothat no overpresentation is required. However, in practice, as hasalready been mentioned above, several selection elements will often bepresented by pushing means which move along the same movementtrajectory, and then, due to the abovementioned deviations in shape andposition, the selection elements will not come into contact with theirstop simultaneously, but one by one and at different points in timeduring this presentation. In order to ensure presentation of allselection elements against their respective stops during the movementtrajectory of the pushing means, overpresentation is required.

Preferably, each selection element is connected at one end to a part ofthe shed-forming device, while the other end is free. In order to limitthe energy required for the overpresentation and the additional frictionand wear associated with overpresentation to a minimum and at the sametime also increase the speed of response of the selection element, theselection element is preferably provided

-   -   with a magnetically influenceable zone which, in the presenting        position, substantially extends opposite the zone of the        associated selector in which the pole surfaces extend, and    -   with a flexible (elastically deformable) zone, whose stiffness        is lower than the stiffness of the magnetically influenceable        zone, and which is situated between the magnetically        influenceable zone and the free end.

If the presenting means exert a mechanical force which acts on theselection element in the vicinity of its free end, the abovementionedflexible zone ensures that the additional deformation of the selectionelement during overpresentation requires very little energy. The verylow stiffness of the flexible zone is achieved by one or more of thefollowing measures: a reduced cross section of the material, theprovision of recesses, holes and/or omission of material.

Preferably, each selection element comprises the following zones, fromthe one to the other end:

-   -   a. a stiff zone in the vicinity of the one end;    -   b. a first flexible zone which has a lower stiffness (resistance        to bending) than the stiff zone, and the flexibility of which        determines the speed of response of the selection element when        the associated selector is actuated in order to bring the        selection element in the deformed or the undeformed position;    -   c. a magnetically influenceable zone with a greater stiffness        than the first flexible zone,    -   d. a second flexible zone which is situated beyond the        magnetically influenceable zone and which has a lower stiffness        than the magnetically influenceable zone, and the flexibility of        which determines the amount of energy which is required in order        to deform a selection element which bears against a stop further        in the direction of the selector; and    -   e. an end zone at the free end, where an end part forms a        contact area for the presenting means.

The cross section of the first flexible zone is substantially determinedaccording to the desired speed of response and the maximum magneticforce which can be exerted on the selection element. The cross sectionof the magnetically influenceable zone is substantially determined bythe maximum magnetic flux through the material, but the desiredstiffness partly determines the ration between the thickness and thewidth of this cross section. The cross section of the second flexiblezone is substantially determined such that the selection element in thiszone has a very low stiffness, so that the overpresentation of selectionelements requires very little energy. The contact area of the end partis preferably relatively large in order to limit wear of the contactareas of the selection elements and the presenting means.

With this shed-forming device, each selection element is at one endpreferably connected to a part of the shed-forming device while theother end is free, with the presenting means and the selection elementbeing movable with respect to one another along the longitudinaldirection of the selection element, and with the presenting meanscomprising at least one first guide flank which is designed in such amanner that the free end of the selection element comes into contactwith the guide flank during the movement and follows this guide flankduring the further movement, so that the free end is pushed in asideward direction and the selection element is deformed.

Using such a shed-forming device, the presentation of a large number ofselection elements can be achieved in an effective manner. Thedeformation achieved by means of this guide flank is preferablysufficient to bring the selection element into the presenting position.

Preferably, the presenting means is secured to a part which can bedriven to perform a reciprocating movement, while the selection elementis attached to a fixed part of the shed-forming device at a fixedheight. Thus, the presenting means may, for example, be connected to orform part of a knife or a shed-forming element, such as a hook. In thiscase, the device can be configured in such a manner that the guide flankof the presenting means strikes against the bottom free end of thefixedly secured selection element during the ascending movement. Duringthe further ascending movement of the presenting means, the free end ofthe selection element slides over the guide flank which is movingupwards and the free end is gradually displaced sideways towards theselector. As a result thereof, the selection element is deformed inorder to bring it into the presenting position. The material from whichthe selection element is made is preferably spring steel.

In a variant embodiment, the situation is reversed: here, the selectionelement is secured to a part which can be driven to perform areciprocating movement, while the presenting element is attached to afixed part of the shed-forming device at a fixed height. Thus, theselection element can, for example, be connected to or form part of ashed-forming element, such as a hook. The device can be configured insuch a manner that the top free end of the flexible selection elementstrikes the guide flank of the fixedly secured presenting means duringthe upward movement. During the further upward movement of the selectionelement, the free end follows the guide flank, as a result of which itis gradually displaced sideways towards the selector. As a resultthereof, the selection element is deformed in order to bring it into thepresenting position.

Preferably, the shed-forming device is configured as having a presentingmeans which comprises a second guide flank which is designed in such amanner that, during the further movement beyond the first guide flank,the free end of the selection element comes into contact with saidsecond guide flank and follows said second guide flank, so that theselection element is first pushed further towards the selector and isdeformed further and then maintains virtually the same deformationduring the further movement.

As mentioned above, the first guide flank ensures that the selectionelement is deformed into the presenting position or in the vicinitythereof. The second guide flank now has a first part which causes anadditional deformation so that the selection element is guaranteed to bepushed against the stop, even with different positioning and/or with adifferent shape or dimensions. For a number of selection elements, thiswill result in overpresentation, as explained above.

Then, there has to be sufficient time to allow the selected shed-formingelements to engage with their hook-engagement means to retain them at afixed height. To this end, the selection elements have to be kept intheir deformed position for a short period of time during the furthermovement of the presenting means or during their own movement withrespect to the presenting means.

In order to achieve this, the second guide flank comprises a second partwhich is designed in such a manner that the free end of the selectionelement comes into contact with this second part during the furthermovement beyond the first part, and follows this second part, so that,during the further movement, the selection element maintains virtuallythe same deformation which has been achieved before. This deformation tobe maintained is preferably the deformation which has been achieved bythe first part.

The first guide flank and the first and the second part of the secondguide flank can be configured as an uninterrupted flank or may consistof two or three part flanks with intermediate breaks. The first part ofthe second guide flank may, for example, together with the first guideflank, form an uninterrupted flank while the second part of the secondguide flank is configured as a separate flank. The separate second guideflank may also only comprise the first or the second part of the flank,with the other part being omitted.

If the second part of the second guide flank on the presenting means hasa small incline with respect to the direction of movement (an inclinewhich is smaller than the incline of the selection element at thatlocation with respect to the direction of movement) or runs parallel tothis direction of movement, then the selection element is deformedfurther during the further movement along this second part, as thecontact point comes to lie increasingly closer to the holding point, butthen the selection element moreover brushes along a very limited zone atthe start of this guide flank with each movement. As the selectionelements are usually made from a harder material than the presentingmeans, this leads to accelerated local wear of the presenting means,leading to a changed presenting position as an additional result.

If a guide flank is provided with a greater angle of inclination (anincline which is slightly greater than the incline of the selectionelement at this location with respect to the direction of movement), theend of the selection element will follow the inclined surface of theguide flank, so that the selection element brushes along the presentingmeans over a longer trajectory. This solves the problem of acceleratedlocal wear. However, this has the drawback that the selection element isdeformed further and unnecessarily during this movement, thusunnecessarily subjecting the presenting means and the stop to load. Thisunnecessary deformation of a large number of selection elementsincreases the energy consumption and the wear of parts.

This drawback is overcome by providing the selection element with aprojection on the side facing the guide flanks, so that only theprojection comes into contact with the first and/or the second guideflank and slides along the surface of said flank during the movement.

The above problem may present itself in any shed-forming device in whicha flexibly or rotatably attached selection element is deformed orrotated by one or more guide flank(s) of a positioning element. In thiscase, the technical measures mentioned in the previous paragraph alsooffer a solution. The present patent application therefore also relatesto a shed-forming device which has the feature mentioned in the aboveparagraph without being provided with the abovementioned featuresaccording to Claims 1 to 20.

In this context, the term projection refers to each laterally projectingportion of the selection element. This may, for example, be athickening, a protuberance or a bending of the material of the selectionelement, but an element which is attached to the selection element isalso seen as a projection in the context of the present invention.

The projection keeps the selection element at a distance from the guideflank. With a guide flank which runs parallel with the direction ofmovement or has a small angle of inclination, the material of theselection element will consequently not only slide along the limitedstarting zone of this flank. The contact is formed by the projection andthis projection can freely slide along the guide flank along a longertrajectory.

Preferably, the second guide flank has at least one part which isvirtually parallel to the direction of the relative movement between theselection element and the presenting means. Such a guide flank makes itpossible to keep the selection element in the same deformed positionduring part of the movement. As has been explained above, this offersthe advantage that the selection element does not have to be deformedunnecessarily during the further relative movement of the presentingmeans and the selection element which is required to ensure engagementof the shed-forming means.

In a preferred embodiment, the selection element has an opening in thevicinity of the free end, so that an edge portion of the presentingmeans which extends between said contact point and the start of theguide flank is situated in said opening when the end of the selectionelement is in contact with a guide flank of the presenting means.

Preferably, this opening is also the hook-engagement opening forenabling the shed-forming elements to be retained. As the edge portionof the presenting means extending along the guide flank can be in theopening, the end can freely remain in contact with the selection elementalong a longer trajectory. This feature is preferably used incombination with the abovementioned projection, but can also be usedwith selection elements without such a projection. Preferably, eachselection element has, at its free end, an end part which is bent at anobtuse angle and extends towards the vertical plane of the selector.

The mutual positions of the cooperating selection elements andpresenting means may vary, for example due to vibrations or differentdimensions or different positions during the installation of parts. Thesurface of the end part facing the presenting means can act as a contactarea for the presenting means. As a result thereof, the presenting meanswill always efficiently come into contact with the selection element inorder to bring the latter into the desired presenting position. Inaddition, the oblique contact area results in a less abrupt contactbetween the presenting means and the selection element. When contacttakes place, the contact area of the selection element will slide alongthe guide surface of the presenting means, so that the impact of thisfirst contact remains limited and the selection element is not, forexample, knocked off.

In a very preferred embodiment, the shed-forming device according to thepresent invention comprises at least one unit which comprises at leasttwo selection elements which extend next to one another from their freeend and are connected to one another at the other end, preferablybecause they are configured as a single entity with a common bridgepart. Such a unit can be fitted and replaced more quickly and easilythan a number of separate selection elements.

The selection means and their associated presenting means are preferablyalso designed in such a manner that at least two groups can bedistinguished, in which, viewed in the same weaving cycle, the point intime at which the selection elements of a group come into contact withtheir respective presenting means differs from the point in time atwhich the selection elements of the other group(s) come into contactwith their respective presenting means.

Due to the fact that the contact between the selection elements andtheir presenting means no longer takes place at the same point in timefor all selection elements, the noise and vibrations in machine partscaused by this contact is also spread out more over time.

Furthermore, it is preferred to provide the shed-forming device with anumber of shed-forming elements with associated hook-engagement meanswhich are provided in order to retain the shed-forming elements at afixed height, and to provide these shed-forming elements andhook-engagement means in such a manner that at least two groups can bedistinguished, in which, viewed in the same weaving cycle, the point intime at which the shed-forming elements of a group engage in theirrespective hook-engagement means differs from the point in time at whichthe shed-forming elements of the other group(s) engage in theirrespective hook-engagement means.

As a result thereof, the instant of contact between shed-formingelements and associated hook-engagement means is spread over time,thereby further reducing the noise pollution and the vibrations inmachine parts.

The present invention furthermore also relates to a method fordetermining the position of elastically deformable selection elements ofa shed-forming device for a weaving machine by means of electromagneticselectors, in which each selection element can, as desired, be placed orheld in an undeformed position or in a deformed position in order todetermine the position of at least one warp thread, and in which, insuccessive weaving cycles, the undeformed selection elements aredeformed under the effect of a mechanical force in the direction of anassociated selector, and the selectors are actuated in order to exert amagnetic force on a number of the selection elements in order to placeor keep these selection elements in the deformed position.

Such a method is known. The drawbacks of this method are identical tothe abovementioned drawbacks of the known shed-forming devices. In orderto overcome these drawbacks and to arrive at a very reliable andenergy-saving method, the undeformed selection elements are mechanicallydeformed into a presenting position in which each selection element iskept at a distance from an associated selector by a stop.

As has already been mentioned above, this patent application alsorelates to a shed-forming device for a weaving machine which does notnecessarily have the above-described features mentioned in Claims 1 to20. Such a shed-forming device then comprises at least one elasticallydeformable or rotatably attached selection element with a free end, anda positioning means in order to bring the selection element into adeformed or rotated position, in which the positioning means and theselection element are movable with respect to one another along thelongitudinal direction of the selection element, and in which thepositioning means comprises at least one guide flank which is designedin such a way that the free end of the selection element comes intocontact with the guide flank during said movement and follows this flankduring the further movement, so that the selection element is brought orheld in a deformed or rotated position.

If the positioning means is provided with a guide flank which has asmall incline with respect to the direction of movement (an inclinewhich is smaller than the incline of the selection element at saidlocation with respect to the direction of movement) or runs parallel tothis direction of movement, the selection element brushes along a verylimited starting zone of this guide flank with each movement. Due to thefact that the selection elements are usually made from a harder materialthan the positioning means, these positioning means are subjected toaccelerated local wear, leading to a different positioning as additionalresult.

If a guide flank with a larger angle of inclination is provided (anincline which is slightly larger than the incline of the selectionelement at said location with respect to the direction of movement), theend of the selection element will follow the inclined surface of theguide flank, so that the selection element brushes along the presentingmeans over a longer trajectory. The problem of accelerated local wear isthus solved. However, the associated drawback is that the selectionelement is unnecessarily deformed further during this movement. Theunnecessary deformation of a large number of selection elementsincreases the energy consumption.

This drawback is overcome by providing the selection element with aprojection on the side facing the guide flank, so that only theprojection comes into contact with the guide flank during the movementand slides along the surface of said flank.

Here, the term projection refers to each laterally protruding portion ofthe selection element. This may, for example, comprise a thickening, aprotuberance or a bending of the material of the selection element, butan element which is attached to the selection element is also regardedas a projection in the context of the present invention.

The selection element is kept at a distance from the guide flank by theprojection. With a guide flank which runs parallel with the direction ofmovement or has a small angle of inclination, the selection element willthus not only slide along the limited starting zone of this flank. Thecontact is formed by the projection and this projection can freely slidealong the guide flank over a longer trajectory.

The usual arrangement of a flexible selection element is such that, whenit has been brought into a position to retain the shed-forming elementby the selector, the selection element is more or less straight from itsbending point up to the attachment point with which the shed-formingelement is retained.

In addition, in an advantageous embodiment, the selection element willalso be more or less parallel to the direction of movement of theshed-forming element due to the movement of the knives. More or lessparallel means that, between bending point and attachment point of theselection elements, the tangent lines on these selection elements in aplane in which a point of the selection element is moved by thepresenting means do not deviate by more than 20 degrees with respect tothe parallel lines in the direction of movement of the shed-formingelement, preferably by not more than 10 degrees and most preferably byless than 5, e.g. 0, 1 or 2 degrees.

This makes it possible to keep the flexural stress in the selectionelement very low and possibly reduce it to 0. In the case of anembodiment comprising a selection element which is not fixedly connectedto the shed-forming element, this also ensures that the selectionelement does not deform to a significant extent under the action of thespring force on the shed-forming element and can, for example, also notbe pulled onto the stop on the selector, as this would unnecessarilysubject the stop to load. In addition, an arrangement in which theselection element is more or less parallel with the direction ofmovement of the shed-forming element due to the movement of the knivesas has been described above, can also offer advantages for theinstallation space which is required for the combination of selectionelements, selectors and shed-forming elements, and thus also for thecompactness of the shed-forming device.

Thus, as has already been mentioned, the above-described shed-formingdevice does not necessarily have the features of Claims 1 to 20, but itshould however be stressed that this shed-forming device may be providedwith one or more of these features, and then obviously obtains theabovementioned effects and advantages as a result.

Preferably, the positioning means comprises a first and a second guideflank which are designed in such a manner

-   -   that, during said movement, the free end of the selection        element first comes into contact with the first guide flank and        follows said flank, so that the free end is pushed in a sideward        direction and the selection element is brought into a deformed        or rotated position, and    -   that, during the further movement, the free end of the selection        element then comes into contact with the second guide flank and        follows said second guide flank so that the selection element is        first deformed or rotated further and is then held in virtually        the same deformed or rotated position during the further        movement.

At least a part of the second guide flank is preferably virtuallyparallel with the direction of the relative movement between theselection element and the positioning means. Such a guide flank allowsthe selection element to be kept in the same deformed or rotatedposition during part of the movement, so that the parts are notunnecessarily subjected to load and unnecessary energy consumption isprevented.

In a preferred embodiment, the selection element comprises an opening inthe vicinity of the end part which is designed such that, when theprojection on the selection element is in contact with a guide flank ofthe presenting means, an edge portion of the presenting means whichextends between this contact point and the start of the guide flank issituated in said opening.

At the free end, the selection element may comprise an end part which isbent at an obtuse angle and directed away from the guide flanks.

The positions of the cooperating selection elements and positioningmeans with respect to one another may vary, for example due tovibrations or different dimensions or different positions duringinstallation of parts. The surface of the end part facing the presentingmeans can serve as a contact area for the presenting means.

As a result thereof, the presenting means will always come into contactwith the selection element in an efficient manner in order to bring thelatter into the desired deformed or rotated position. In addition, theoblique contact area results in a less abrupt contact between thepresenting means and the selection element. When contact takes place,the contact area of the selection element will slide along the guidesurface of the presenting means, so that the impact of this firstcontact remains limited and the selection element is not, for example,knocked off.

The selection element may be provided with a hook-engagement openinginto which a projection of a shed-forming element or of a fixedlyarranged part can engage. However, the reverse situation in which theselection element comprises a projection which is designed to engage ina hook-engagement opening of a shed-forming element or of a fixedlyarranged part is also possible. Said projection is preferablyhook-shaped.

The abovementioned guide flanks may also be provided on the selectionelement. The presenting means then comprises, for example, a straightflank by means of which it makes contact with the guide flank on theselection element. During the movement of the presenting means and theselection element with respect to one another, the selection elementwill be pushed in a lateral direction and deformed in this embodiment aswell.

In the following description, some preferred embodiments and parts of ashed-forming device according to the invention will be described in moredetail. The sole intention of this detailed description is to indicatehow the invention can be achieved and to illustrate and, wherenecessary, explain the operation and the particular features thereof.This description can therefore not be regarded as a limitation of thescope of protection of this patent and neither can the area ofapplication of the invention be limited on the basis of thisdescription.

In this description, reference is made to the attached figures, in which

FIGS. 1 to 6 diagrammatically show a flexible holding element togetherwith an electromagnetic selector and a hook with presenting means, inwhich

FIGS. 1 to 4 show the successive phases during presentation of theholding element by means of the upwardly moving hook,

FIG. 5 shows the situation in which the hook is retained at a fixedheight by the selection element, and

FIG. 6 shows the situation in which the hook is not retained at a fixedheight;

FIGS. 7 to 12 show the same as FIGS. 1 to 6, the only difference beingthat the end of the holding element is now provided with a projectionwhich makes contact with the guide flanks of the hook;

FIGS. 13, 14 and 15 in each case diagrammatically show the same fourselection elements together with a respective selector and a hook withpresenting means, these figures representing three successive phasesduring the presentation of the selection elements;

FIGS. 16 to 19 show diagrammatic representations of a flexible holdingelement together with an electromagnetic selector and a hook withpresenting means, the figures only differing from one another by thefact that the stop is provided at another location on the selector;

FIGS. 20 and 21 show diagrammatic representations of a selection elementwhich forms part of an up and down moving hook together with anelectromagnetic selector and an engagement means, the stop beingprovided on the selector (FIG. 20) or on the selection element (FIG.21), respectively;

FIGS. 22 and 23 show a diagrammatic representation of a fixedly securedflexible holding element together with an electromagnetic selector and aup and down moving hook, the stop being provided on the selector (FIG.22) or on the selection element (FIG. 23), respectively;

FIG. 24 shows a diagrammatic representation of a fixedly securedflexible holding element together with an electromagnetic selector and aup and down moving hook with presenting means, the holding element beingconnected to a chassis part of the shed-forming device;

FIGS. 25, 26 and 27 show a perspective view, a front view and a sideview, respectively, of a unit with six selection elements;

FIG. 28 shows a detail view of the circled portion of the selectionelements on the side view from FIG. 27;

FIGS. 29 and 30 show a diagrammatic representation of a selectionelement which forms part of a up and down moving hook together with anelectromagnetic selector and engagement and presenting means which aredesigned as a single piece (FIG. 29) and as separate parts (FIG. 30),respectively.

In the arrangements which are diagrammatically shown in FIGS. 1 to 19,the selection element (1) is in each case designed as a thin stripconsisting of flexible and elastically deformable material, the upperend (11) of which is attached to a fixed part (12) of the shed-formingdevice. This selection element (1) is attached in such a manner that itextends to the left of the vertical direction (V) at a small angle. Onthe left-hand side of the selection element, there is a fixed supportingelement (5). If no forces are exerted on the selection element (1), theselection element (1) is forced against this fixed supporting element(5) due to its elasticity, as a result of which it is under a slightprestress which counteracts a deformation to the right. The supportingelement (5) ensures that the position of the selection element (1) withrespect to the other parts, in particular the presenting means (3), isguaranteed.

At its free end, the selection element (1) has an end part (6) which isbent to the right at an obtuse angle, and has a hook-engagement opening(7) in the vicinity of this end part into which the head portion (18) ofa hook (3) can engage.

The hook (3), only the upper end of which is illustrated, cooperateswith known shed-forming means (not shown in the figures) so as toposition one or more warp threads in each weaving cycle with respect tothe level at which pick threads are introduced in a weaving machine. Tothis end, the hook (3) is caught by a up and down moving knife (notshown) and at the same time held in its vertical movement path by guidemeans (8).

Above the hook-engagement opening (7), the selection element (1) has aclosed part (9) made of magnetically influenceable material which issituated opposite the force-exerting pole surfaces (10) of anelectromagnetic selector (2). The electromagnetic parts of the selector(2) are illustrated diagrammatically in the figures by a hatchedrectangle, so that the force-exerting pole surfaces (10) arediagrammatically represented in the drawings by the left-hand verticalside of this rectangle. The zone in which the pole surfaces aresituated, also referred to as the pole zone, is the zone which extendsbetween the edges of the pole surface or of the plurality of polesurfaces which are furthest apart. The space between the two paralleltransverse planes (A),(B) which coincide with these edges which arefurthest apart is the space in which the stop (4) is preferablyprovided. The intermediate distance between these transverse planes (A,B) denoted in FIG. 1 with the letter w.

In the figures, except for FIGS. 16 to 19, the stop (4) is arrangedcentrally in the pole zone, in the central part between the boundarysurfaces (C, D) with an intermediate distance (w/2) which is half theintermediate distance (w) between the abovementioned transverse planes(A, B). The intermediate distance between the transverse planes (A,B)and the closest boundary surfaces is then approximately equal to anintermediate distance w/4.

The stop (4) is provided on the selector (2) in the embodiments fromFIGS. 1 to 19, 20, 22, 24, 29 and 30. In the embodiments according toFIGS. 21 and 23, the stop is provided on the selection element (1). Ineach case, the stop (4) is provided with a contact area which has aconvex shape in a vertical cross section.

The upper portion of the hook (3) is provided with guide flanks(13),(14),(15) to push the selection element (1) towards the selector(2), in other words to present it, during its upward movement. Thus, thehook (3) here serves as a presenting means. The upper portion of thehook (3) is also provided with a recess (16) which is limited at the topby a hook-shaped edge (17). As is explained further with reference toFIG. 5, it is this hook-shaped edge (17) with which the hook (3) willrest on the bottom edge (7 a) of the hook-engagement opening (7) of theselection element (1) when it engages in the hook-engagement opening(7).

During the upward movement of the hook (3), the front guide flank (13)thereof strikes against the end part (6) on the free end of theselection element (1). The instant at which contact is made, isillustrated in FIG. 1. As the hook (3) is moved upwards further, the endpart (6) slides further along this guide flank (13), as a result ofwhich the end part (6) is pushed towards the selector (2) and theselection element (1) is deformed.

During the further upward movement of the hook (3) (see FIG. 2), the endpart (6) beyond the recess (16) comes into contact with the second guideflank (14, 15). A first part (15) of this second guide flank—the partwhich delimits the recess (16) at the bottom—pushes the selectionelement (1) further towards the selector (2), as a result of which theselection element is deformed further. This further deformation beyondthe first contact with the stop (4) is carried out in order to ensurethat all selection elements (1) are brought into the presenting positionin which they bear against a respective stop (4). This so-called‘overpresenting’ is illustrated more clearly with reference to FIGS. 13to 15.

During the further upward movement of the hook (3), the bottom end part(6) of the selection element (1) comes into contact with the second part(15) of the second guide flank (14, 15), as is illustrated in FIG. 3.The further upward movement of the hook (3) is necessary in order tobring the hook into a position in which its head portion (18) is broughtsufficiently far beyond the bottom edge (7 a) of the hook-engagementopening (7) of the selection element (1) in order to ensure that thishead portion (18) readily enters the hook-engagement opening (7) at thestart of the downward movement of the hook (3) when the associatedselection element (1) is not attracted by the selector and springs back.The head portion (18) is the portion from the top end of the hook whichis delimited by the hook-shaped edge (17) at the bottom, and which, inside view, has a virtually triangular shape.

The second portion (15) of the second guide flank (14, 15) is inclinedwith respect to the vertical direction (V). This angle of inclinationhas to be greater than the incline of the selection element (1) in thislocation, so that the bottom end part (6) of the selection element (1)can freely follow the inclined guide surface (15) until it reaches theposition which is shown in FIG. 4. This causes a further deformation ofthe selection element (1), until the hook has reached its outermostpoint, as imposed by the movement of the knives.

The selector (2) is actuated in order to optionally attract theselection element (1). An electrical current is passed through theselector coil in order to attract the selection element (1) and hold itin a position against the stop (4). This excitation of the selector coilcan already start before the presentation and overpresentation haveended.

If the selection element (1) is not attracted by the selector (2) (seeFIG. 5), it springs back to the position from FIG. 1 when the hook movesback down. In this case, the head portion (18) of the hook (3) ends upin the hook-engagement opening (7) of the selection element. As the hook(3) is moved further down, it ultimately reaches the position from FIG.5, in which the hook-shaped edge (17) rests on the bottom edge (7 a) ofthe hook-engagement opening (7).

However, if the selection element (1) is attracted (see FIG. 6), thehook (3) is not able to engage in the hook-engagement opening (7) of theselection element (1) during its downward movement, so that it followsthe knife moving downward. If a hook does engage in the hook-engagementopening, it will partially follow the above cycle, after the downwardmovement and in the movement back up of the associated knife. Theassociated knife will catch the hook, so that it moves further upwards,beyond the engagement point of the selection element, as a result ofwhich the latter beyond the recess finally comes in contact with thefirst part (14) of the second guide flank (14, 15), with a path andassociated selection options as already described above for a hook whichhas followed the entire movement of the knife.

According to the present invention, an embodiment has also beendeveloped which prevents the unnecessary further deformation of thesecond guide flank (14, 15) by the second part (15). This is illustratedby means of FIGS. 7 to 12 which show the same situations as FIGS. 1 to6.

In order to prevent the additional deformation of the guide flank by thesecond part (15), this flank part (15) has to run virtually parallelwith the direction of movement (V) of the hook (3).

In order to ensure that the end part (6) of the selection element (1)can slide along this flank part (15) during the entire trajectory of thefurther movement, a projection (19) facing the guide flank (14, 15) isprovided on the end part (6) of the selection element (1). Theprojection (19) is formed by bending the selection element (1), towardsthe free end, away from the selector and making the last end portion runback obliquely to the selector (2). The projection is formed by thematerial facing the guide flanks (13), (14, 15) in the bend which isthus formed.

In FIG. 10, an arrow (P) indicates the location where an edge portion ofthe hook (3) extending along the flank (15) is situated in thehook-engagement opening (7) of the selection element (1) when the endpart (6) provided with the projection (19) slides along this guide flank(15). In order to prevent a decrease or wear of the material, thelocation, the shape and the size of the hook-engagement opening (7) havebeen determined in such a manner that the edges of the opening (7)cannot come into contact with the material of the hook (3) at any pointin time.

FIGS. 13 to 15 in each case show four selection elements (1 a), (1 b),(1 c), (1 d) which are arranged at a fixed height and belong to the sameshed-forming device at the same point in time together with a respectiveselector (2 a), (2 b),(2 c),(2 d) and a respective hook (3 a),(3 b),(3c),(3 d) with guide flanks (13, 14, 15).

In each of FIGS. 13, 14 and 15, these four selection elements (1 a),(1b), (1 c),(1 d) are shown at a different (subsequent) point in timeduring the movement. However, as a result of mutual differences inpositioning, dimensions, actions of forces, etc., the selection elements(1 a),(1 b),(1 c),(1 d) are not in the same position with respect to theguide flanks (13, 14, 15) at the same point in time during the movementand are therefore also not in the same position with respect to the stop(4). Thus, the selection element (1 a) which is furthest to the left isnot yet in contact with the hook (3 a) at the point in time of FIG. 13,whereas the other three selection elements (1 b),(1 c),(1 d) of FIG. 13are in contact with the hook (3 a) at that point in time.

Thus, it can also be seen that the selection element (1 d) which isfurthest to the right is already in contact with the stop (4) at thepoint in time of FIG. 14, whereas this is not yet the case for the otherselection elements (1 a), (1 b), (1 c) at that point in time.

All selection elements are deformed further by the guide flanks (13),(14) during the further movement after the point in time shown in FIG.14 until they have all been brought against their respective stop (4) atthe point in time shown in FIG. 15. As the selection element (1 d) whichis furthest to the right at the point in time shown in FIG. 14 wasalready in contact with the stop (4), this selection element (1) isoverpresented during its further displacement by the first part (14) ofthe second guide flank (14, 15).

Since the second part (15) of this second guide flank (14, 15) runsparallel with the direction of movement (V), the selection elements (1a), (1 b), (1 c), (1 d) are not deformed further by this flank part(15).

In FIGS. 16 to 19, with the above-described embodiment of a fixedlysecured selection element (1) together with an electromagnetic selector(2) and a hook (3) with guide surfaces (13,14,15), the stop (4) isprovided at different positions on the selector. In the embodimentillustrated in FIG. 16, the stop (4) is situated in a central positionbetween the transverse planes (A),(B) which delimit the zone of the polesurfaces (10). In FIGS. 17 and 18, this is a position near the top (A)and the bottom transverse plane (B), respectively, while FIG. 19 showsthat this position may also be situated outside the space between saidtransverse planes (A),(B).

In FIGS. 20 and 21, a selection element (1) is shown which is the upperportion of a hook which can be moved up and down by a knife (not shown)between guide means (36), (37), together with an electromagneticselector (2) and an engagement means (21) arranged at a fixed height. InFIG. 20, the stop (4) is provided on the selector, whereas in FIG. 21,the stop (4) is provided on the selection element (1).

The selection element (1) has a hook-engagement opening (23), while theengagement means (21) comprises a hook-shaped projection (22). Theselection element (1) can be pushed in the direction of the selector (2)and into a presenting position by means of presenting means (not shown).In the case of FIG. 20, the selection element (1) bears against the stop(4). In the case of FIG. 21, the stop (4) of the selection element bearsagainst the selector (2). In both cases, the hook-shaped projection (22)is situated in the hook-engagement opening (23).

A selection element (1) which is attracted by the selector (2) will hookonto the hook-shaped projection (22) during its downward movement. Aselection element (1) which is not attracted by the selector (2), willspring back into its original position in which the hook-shapedprojection (22) is no longer situated in the hook-engagement opening(23) and will move concomitantly with the knife (not shown) during itsdownward movement.

FIGS. 22 and 23 show a selection element (1) which is arranged at afixed height, together with a up and down moving hook (3) and anelectromagnetic selector (2). In the embodiment from FIG. 22, the stop(4) is provided on the selector (2), whereas in the embodiment from FIG.23, the stop (4) is provided on the selection element (1). The selectionelement (1) has a hook-engagement opening (7), while the hook (3)comprises a hook-shaped head (24). The selection element (1) can bepushed in the direction of the selector (2) and into a presentingposition by presenting means (not shown). In the case of FIG. 22, theselection element (1) then bears against the stop (4). In the case ofFIG. 23, the stop (4) of the selection element then bears against theselector (2). In both cases, the hook-shaped head (24) is then not inthe hook-engagement opening (7).

If the selection element (1) has been attracted by the selector (2), thehook (3) will not be able to engage in the hook-engagement opening (7)and be carried along by the knife during its downward movement. If theselection element (1) is not attracted by the selector (2), it willspring back to a position in which the hook-shaped projection (24) issituated in the hook-engagement opening (7). During the downwardmovement of the knife (not shown), the hook-shaped head (24) will engagein the hook-engagement opening (7) and the hook (3) will be held at afixed height. In this case, the hook-shaped head (24) rests on thebottom edge (7 a) of the hook-engagement opening (7).

FIG. 24 shows a selection element (1) together with an electromagneticselector (2) and a up and down moving hook (3) with guide flanks (13),(14, 15), as has been described above with reference to FIGS. 1 to 12.The selection element (1) of the embodiment from FIG. 24 is attached toa fixing element (25) which is attached to the chassis (27) of thejacquard machine by means of a bolt (26). The forces which are exertedon the hooks (3) by the warp threads and the retracting springs aretransferred to a chassis part (27) via the selection elements (1) andnot to the selector (2) or another part of the selection device.

It is possible to provide units (28) comprising more selection elements(28 a-28 f) in the shed-forming device according to the presentinvention. Thus, it is possible to produce a number of adjacentselection elements from the same piece of sheet-shaped material. Such asingle-part component (28) with six selection elements (28 a),(28 b),(28c),(28 d),(28 e),(28 f) is illustrated in FIGS. 25 to 28.

The six selection elements are made in three different lengths, so thatthe selection elements can come into contact with their respectivepresenting means at different points in time during the same weavingcycle. Spreading this instant of contact over time reduces noisepollution and vibrations in the parts of the device.

For the different selection elements (28 a)-(28 f) of a unit, therespective bottom edges (7 a) of the hook-engagement openings (7) arealso provided on three different levels. As a result thereof, the hooksassociated with these selection elements will engage in thesehook-engagement openings (7) at different points in time during the sameweaving cycle. The contact between the hook-shaped edges or projectionsof the hooks and the bottom edges (7 a) of the hook-engagement openings(7) is thus also spread over time, further reducing noise pollution andvibrations.

Two series of selection elements (28 a-28 c),(28 d-28 f) are providednext to one another, each series successively comprising a firstselection element (28 a), (28 d) whose length is shortest and whose edge(7 a) is at the highest level, a second selection element (28 b), (28 e)which is slightly longer and whose edge (7 a) is situated lower comparedto that of the first selection element, and a third selection element(28 c),(28 f) which is longer still and whose edge (7 a) is situatedlower compared to the second selection element. In FIGS. 27 and 28, thethree different lengths can be seen most clearly.

Each unit (28) consists of six selection elements (28 a)-(28 f) whichare adjacent to one another in the same plane and which have a commonbridge part (29) at their upper end so that they form a single entity.Openings (30) are provided in this bridge part (29) at their upper endfor attaching the unit (28) to a fixed part of the shed-forming device.

Five different zones (a-e) can be distinguished on the selectionelements (1):

-   -   a stiff zone (a) in the vicinity of the end which has to be        fixedly attached, in this case the bridge part (29);    -   a first flexible zone (b) which has a lower stiffness than the        stiff zone (a), and whose flexibility determines the speed of        response of the selection element when actuating the associated        selector in order to bring the selection element in the deformed        or the undeformed position;    -   a magnetically influenceable zone (c) with a greater stiffness        than the first flexible zone (b);    -   a second flexible zone (d) which is situated beyond the        magnetically influenceable zone (c), and which has a lower        stiffness than the magnetically influenceable zone (c), and        whose flexibility determines the amount of energy which is        required to deform a selection element (28 a)-(28 f) bearing        against a stop (4) further in the direction of the selector (2);        and    -   an end zone (e) on the free end where an end part (6) which is        bent at an obtuse angle forms a contact area for the presenting        means.

The embodiment illustrated in FIGS. 29 and 30 comprises a flexible andelastically deformable selection element (1) which forms the upperportion of a up and down moving hook together with an electromagneticselector (2) and engagement and presenting means provided at a fixedheight. In the embodiment from FIG. 29, the presenting means (3) arearranged at a fixed height and the hook-engagement means areincorporated in the same part (3). A hook-shaped edge (30) acts asengagement means, while the guide flanks (31), (32) ensure presentationof the selection element (1). The selection element (1) comprises ahook-engagement opening (33) and an upper free end which is providedwith a projection (19) which is directed towards the guide flanks (31),(32) and an end part (6) which is bent at an obtuse angle and isdirected obliquely, away from these guide flanks (31),(32).

If the selection element (1) is attracted by the selector (2), it cannothook onto the hook-shaped edge (30) by means of the hook-engagementopening (33) and the hook moves concomitantly with the downwardly movingknife. If the selection element (1) is not attracted by the selector(2), then it can hook onto this edge (30).

In the embodiment according to FIG. 30, the fixedly secured presentingmeans (3) has a continuous guide flank (34) and does not comprise anyhook-engagement means, since the hook-engagement means, in the form of ahook-shaped projection (36), are provided on a separate part (35) whichis also arranged at a fixed height.

When the selection element (1) is attracted, the selection element willengage in the hook-shaped projection (36) by means of thehook-engagement opening (33), so that the hook is held at a fixedheight. If the selection element (1) is not attracted, it will notengage in the projection (36) and will move concomitantly with thedownwardly moving knife.

1. Shed-forming device for a weaving machine comprising a number ofelastically deformable selection elements, it being possible tooptionally place each selection element in an undeformed position or ina deformed position in order to determine the position of at least onewarp thread, a number of electromagnetic selectors which can be actuatedin order to place or keep each selection element in successive weavingcycles in one of said positions, so that the warp threads are positionedin accordance with a predetermined weaving pattern, and presenting meanswhich are designed to exert a mechanical force on a number of undeformedselection elements in each weaving cycle, as a result of which saidselection elements are deformed in the direction of an associatedselector (2), wherein the presenting means are designed to mechanicallydeform the selection elements until they reach a presenting position inwhich they are kept at a distance from an associated selector by a stop.2. Shed-forming device for a weaving machine according to claim 1,characterized in that the shed-forming device comprises at least onereciprocating knife and a number of shed-forming elements which can becaught by a knife in successive weaving cycles in order to change theposition of one or more warp threads, in that each selection element isarranged at a fixed height and is designed to retain an associatedshed-forming element at a fixed height, and in that each selectionelement is designed to, in the one position, retain the associatedshed-forming element at a fixed height and, in the other position, notto retain said shed-forming element and allow it to move along with aknife.
 3. Shed-forming device for a weaving machine according to claim1, characterized in that the shed-forming device comprises at least onereciprocating knife, in that each selection element forms part of ashed-forming element which can be caught by a knife to successiveweaving cycles in order to change the position of one or more warpthreads, and in that each shed-forming element is designed to beretained at a fixed height in the one position of the selection elementand to be caught by a knife in the other position of the selectionelement.
 4. Shed-forming device for a weaving machine according to claim1, characterized in that the respective selectors are provided with astop having a contact area which faces an associated selection element,so that each selection element bears against the contact area of a stopof an associated selector when it is placed in the presenting positionand is thus kept at a distance from a pole surface of said selector. 5.Shed-forming device for a weaving machine according to claim 1,characterized in that the respective selection elements are providedwith a stop having a contact area facing the associated selector, sothat each selection element, when it is placed in the presentingposition, bears against an associated selector with the contact area ofits stop and is thus kept at a distance from a pole surface of saidselector.
 6. Shed-forming device for a weaving machine according toclaim 1, characterized in that each selector comprises one or moreforce-exerting pole surfaces, which extend in a pole zone which isdelimited by two parallel transverse planes, and in that each stop isplaced in such a manner that its contact area is situated in the spacebetween said transverse planes.
 7. Shed-forming device for a weavingmachine according to claim 6, characterized in that each stop is placedin such a manner that its contact area is situated in a central part ofsaid space, with said central part lying centrally between saidtransverse planes and being delimited by two parallel boundary surfaceshaving an intermediate distance (w/2) which is half the intermediatedistance (w) between said transverse planes.
 8. Shed-forming device fora weaving machine according to claim 4, characterized in that thecontact area of the stop is a substantially convex curved surface. 9.Shed-forming device for a weaving machine according to claim 1,characterized in that each selection element is connected at one end toa part of the shed-forming device, while the other end is free, in thateach selection element comprises a magnetically influenceable zonewhich, in the presenting position, substantially extends opposite thezone of the associated selector in which the pole surfaces extend, andin that each selection element comprises, between the magneticallyinfluenceable zone and the free end, a flexible zone whose stiffness islower than the stiffness of the magnetically convex curved zone. 10.Shed-forming device for a weaving machine according to claim 9,characterized in that each selection element comprises the followingzones, from the one to the other end: a. a stiff zone in the vicinity ofthe one end, b. a first flexible zone which has a lower stiffness thanthe stiff zone, and the flexibility of which determines the speed ofresponse of the selection element when the associated selector isactuated in order to bring the selection element in the deformed or theundeformed position; c. a magnetically influenceable zone with a greaterstiffness than the first flexible zone; d. a second flexible zone whichis situated beyond the magnetically influenceable zone and which has alower stiffness than the magnetically influenceable zone, and theflexibility of which determines the amount of energy which is requiredin order to deform a selection element which bears against a stopfurther in the direction of the selector; and e. an end zone at the freeend, where an end part forms a contact area for the presenting means.11. Shed-forming device for a weaving machine according to claim 1,characterized in that each selection element is at one end connected toa part of the shed-forming device while the other end is free, in thatthe presenting means and the selection element are movable with respectto one another along the longitudinal direction of the selectionelement, in that the presenting means comprises at least one first guideflank which is designed in such a manner that the free end of theselection element comes into contact with the guide flank during themovement and follows said guide flank during the further movement, sothat the free end is pushed in a sideward direction and the selectionelement is deformed.
 12. Shed-forming device tor a weaving machineaccording to claim 11, characterized in that the presenting meanscomprises a second guide flank which is designed in such a manner that,during the further movement beyond the first guide flank, the free endof the selection element comes into contact with said second guide flankand follows said second guide flank, so that the selection element isfirst pushed further towards the selector and is deformed further andthen maintains virtually the same deformation during the furthermovement.
 13. Shed-forming device for a weaving machine according toclaim 12, characterized in that the selection element comprises aprojection on the side facing the guide flanks, so that only theprojection comes into contact with the first and/or the second guideflank and slides along the surface of said flank during the movement.14. Shed-forming device for a weaving machine according to claim 12,characterized in that at least one part of the second guide flank isvirtually parallel with the direction of the relative movement betweenthe selection element and the presenting means.
 15. Shed-forming devicefor a weaving machine according to claim 11, characterized in that theselection element has an opening in the vicinity of the free end, sothat an edge portion of the presenting means which extends between saidcontact point and the start of the guide flank is situated in saidopening when the end of the selection element is in contact with a guideflank of the presenting means.
 16. Shed-forming device for a weavingmachine according to claim 11, characterized in that each selectionelement has, at its free end, an end part which is bent at an obtuseangle and extends towards the vertical plane of the selector. 17.Shed-forming device for a weaving machine according to claim 1,characterized in that the shed-forming device comprises at least oneunit which comprises at least two selection elements, which extend nextto one another from their free end and are connected to one another atthe other end, preferably because they are configured as a single entitywith a common bridge part.
 18. Shed-forming device for a weaving machineaccording to claim 1, characterized in that the selection elements andtheir associated presenting means are designed in such a manner that atleast two groups can be distinguished, in which the point in time atwhich the selection elements of a group come into contact with theirrespective presenting means differs from the point in time at which theselection elements of the other group(s) come into contact with theirrespective presenting means.
 19. Shed-forming device for a weavingmachine according to claim 1, characterized in that the shed-formingdevice comprises a number of shed-forming elements with associatedhook-engagement means which are provided in order to retain the shedforming elements at a fixed height, and in that said shed-formingelements and hook-engagement means are provided in such a manner that atleast two groups can be distinguished, in which the point in time atwhich the shed-forming elements of a group engage in their respectivehook-engagement means differs from the point in time at which theshed-forming elements of the other group(s) engage in their respectivehook-engagement means.
 20. Method for determining the position ofelastically deformable selection elements of a shed-forming device for aweaving machine by means of electromagnetic selectors, in which eachselection element can, as desired, be placed or held in an undeformedposition or in a deformed position in order to determine the position ofat least one warp thread, and in which, in successive weaving cycles,the undeformed selection elements are deformed under the effect of amechanical force in the direction of an associated selector, and theselectors are actuated in order to exert a magnetic force on a number ofthe selection elements in order to place or keep these selectionelements in the deformed position, wherein the undeformed selectionelements are mechanically deformed into a presenting position in whicheach selection element is kept at a distance from an associated selectorby a stop.
 21. Shed-forming device for a weaving machine comprising atleast one elastically deformable or rotatably attached selection elementwith a free end, and a positioning means in order to bring the selectionelement into a deformed or rotated position, in which the positioningmeans and the selection element are movable with respect to one anotheralong the longitudinal direction of the selection element, and in whichthe positioning means comprises at least one guide flank which isdesigned in such a way that the free end of the selection element comesinto contact with the guide flank during said movement and follows thisflank during the further movement, so that the selection element isbrought or held in a deformed or rotated position, characterized in thatthe selection element comprises a projection on the side facing theguide flank(s), so that only the projection comes into contact with theguide flank during the movement and slides along the surface of saidflank.
 22. Shed-forming device for a weaving machine according to claim21, characterized in that the positioning means comprises a first and asecond guide flank which are designed in such a manner that, during saidmovement, the free end of the selection element first comes into contactwith the first guide flank and follows said flank, so that the free endis pushed in a sideward direction and the selection element is broughtinto a deformed or rotated position, and that, during the furthermovement, the free end of the selection element then comes into contactwith the second guide flank and follows said second guide flank so thatthe selection element is first deformed or rotated further and is thenheld in virtually the same deformed or rotated, position during thefurther movement.
 23. Shed-forming device for a weaving machineaccording to claim 22, characterized in that at least a part of thesecond guide flank is virtually parallel with the direction of therelative movement between the selection element and the positioningmeans.
 24. Shed-forming device for a weaving machine according to claim21, characterized in that the selection element comprises an opening inthe vicinity of the end part which is designed such that, when theprojection on the selection element is in contact with a guide flank ofthe positioning means, an edge portion of the positioning means whichextends between said contact point and the start of the guide flank issituated in said opening.
 25. Shed-forming device for a weaving machineaccording to claim 21, characterized in that, at the free end, theselection element comprises an end part which is bent at an obtuse angleand directed away from the guide flanks.